This invention relates to electrical circuit breakers and, more particularly, to electrical circuit breakers including a flexible electrical connector connected to a moving contact piece having a contact face arranged to make or break contact with a contact face on a relatively fixed contact piece to make or break an associated electrical circuit the respective contact faces extending generally perpendicular to the direction of movement of the moving contact piece.
One of the main considerations in the design of any circuit breaker is to ensure that sufficient pressure is applied to the current carrying contact faces by contact loading springs, in order to avoid welding together of the contact faces during a fault condition in the associated circuit. When an overload fault current flows through the contact faces a large amount of heat is produced. Dependent upon the design and type of contacts used and particularly with butt type contacts employed in vacuum interrupters there is usually a "blow-open" force involved. This is the electromagnetic force created by the fault current which tends to act to urge apart the contact faces, reducing the contact pressure, which increases the resistance and leads to further heating or even initial contact face separation and arcing. This heating or arcing can cause welding together of the contact faces. If welding occurs the circuit breaker opening mechanism will experience difficulty in separating the contact faces after the passage of a fault current and even may fail to interrupt the fault current.